For several decades, orthodontists and periodontists have repeated that orthodontics have no harmful consequences on the periodontium when it is healthy or treated. However, a systematic review of the literature undermines this common refrain and concludes that there is a lack of reliable evidences of the positive effects of orthodontics on periodontal health with, in the best periodontal conditions, slight adverse effects. It is therefore the responsibility of orthodontists to keep the periodontal cost of orthodontic treatment as low as possible. How to make sure that this « at best » does not turn into an « at worst » ? In order to minimize the deleterious consequences of orthodontic treatment on the periodontium, the orthodontist must be able to specify which patients she/he can immediately consider providing orthodontic treatment and those on whom periodontal treatment is mandatory before all. The orthodontist must therefore transform, for a few minutes, into a periodontist in order to recognize the eight signs of loss of attachment and the six risk factors for periodontitis, exposed in this article. Both needs for periodontal and orthodontic treatment have to be measured and would not be efficient without the patient's and the practitioners' motivation.In 2018, a new « Classification of Periodontal and Peri-implant Diseases and Conditions » was adopted by the American Academy of Periodontology and the European Federation of Periodontology. Numerous studies in recent years have improved the understanding of periodontal diseases and their risk factors, leading to an update of the 1999 classification. Among the major changes is the development of a classification of periodontitis into different stages and grades and the notion of periodontal health, an essential prerequisite for orthodontic treatment. Based on the analysis of the 24 published articles, this work provides explanations regarding the main changes that orthodontists may face. ART899 mouse The classification of Chicago precisely defines periodontal health and proposes a new system for characterizing periodontitis in stages and grades. It then becomes a valuable aid for the orthodontist in risk detection and periodontal screening. The knowledge of this new classification is essential for reliable communication between dentists, periodontists and orthodontists, in order to guarantee the success of orthodontic treatment.Class III dysmorphia, classically distributed in hereditary or functional etiology, have often multifactorial causes. Breaking the dysmorpho-dysfunctional cascade with early treatment may seem to be an essential alternative to give growth a new orientation. Whether the treatments are preventive, interceptive with or without an appliance, orthodontic or surgical (early, first-line or late), this takes more account of the clinical form than of age. The authors, through clinical cases, will develop their therapeutic approach, based on clinical common sense. Waiting to act at the right time is essential to set up treatments based on proven therapies.Artificial Intelligence (AI) consists of setting different technics together aimed at allowing machines to simulate human cognitive fonctions, mimic human brain functions, sometime its logic, when it comes to answer to an interrogation, to take decisions or to anticipate events. This new fonction, after being used in numerous daily life domains (geo-guides, personal assistants, administratif procedures) comes now in the medical area. The press exaggerations on those systems doesn't have any wise and thoughtful judgment. This article will talk about the question of the real uses and expertise capacities which the AI should be able to provide in our area. Through the history of cognitive science and ideas, the recension of important works on the AI developments, we want to put in perspective the promises and opportunities provided to modify or complete the expertise in orthodontics. The willingness to extend cognitive and action abilities is older than what the comma historiography of the AI let us think. The recent development of computer systems, algorithmic science and databases allowed the development of a branch of the artificial intelligent giving, in some cases, seemingly undeniable results which should not be extrapolated because of the weakness of our databases, the current economic model and their real use.When performed several times over the course of an orthodontic or surgical orthodontic treatment, three-dimensional (3D) imaging like CBCT or CT-Scans can be superimposed. The purpose of this article is to illustrate the implementation of voxel-based 3D superimpositions with a clinical case of mandibular distraction osteogenesis A 13-year old patient underwent a surgical orthodontic treatment with a « 3D » mandibular distractor. He presented a bilateral atrophy of his mandibular condyles due to a staphylococcus aureus bacteremia at birth. 3D general and mandibular regional superimpositions were performed using CT-Scan and CBCT images acquired respectively before and after completion of the distraction osteogenesis. Two superimposition methods were used, one relying on commercially-available software and the other one relying on a series of « open-source » softwares. Using commercially-available software, 3D superimpositions were automatically performed in a few minutes by a sparsely-trained operator. The method relying on « open-source » software asked for more training and time. Results of the superimpositions were presented under various formats. Evaluation of 3D superimposition results is still challenging, as only a qualitative evaluation can be easily performed. In years to come, this interpretation should however become more straightforward for clinicians.With the conventional 2D exam of clinical cases, the diagnosis is penalized by the lack of data, not only for vertical or transverse or asymmetrical problems, but for classical cases of anteroposterior dysharmonies. In these cases, the effectively used parameter, ANB angle, seems insufficient. So the authors elaborated a 3D biometry tool. The program of morphological analysis is able to deliver a complete description of dysharmony, supported by Cone Beam data capture. In the first part of this article the authors present the foundation of the model anatomical reference, skeletal landmarks, teeth location by inertia matrix calculus, parameters, diagnosis and aid to treatment plan. The second part is the presentation, step by step, of the program in function, analyzing a great case of Class II hyperdivergent, border line surgery. All along the diagnosis way, the authors make the assistant discover all the documents given by the computer about complete 3D diagnosis and aid to treatment plan.